FORAGE CROP MATURITY ZONATION IN THE ATLANTIC REGION USING GROWING DEGREE-DAYS

Accumulated growing degree-days above 5.degree. C (GDD) were used to estimate the average time of occurrence of maturity stages before 1st harvest in post seeding years for alfalfa (Medicago sativa L.), double cut red clover (Trifolium pratense L.) and timothy (Phleum pratense L.) in the Atlantic region of Canada. Maturity stages recommended for 1st cut were reached after an average accumulation of .apprx. 350, 400 and 450 GDD, depending upon the cultivar. Estimates of maturity dates based on the average air temperature (T) for May and June were highly correlated with annually observed dates of selected maturity stages (0.98 .gtoreq. r2 .gtoreq. 0.41). T was also used to estimate regional variation in maturity dates based on normals for the 1951-1980 period from 231 climate stations. Eight maturity zones (M1-M8) were designated for the region. Estimated average dates when forage cultivars reach maturity stages recommended for 1st cut ranged from on or before 15 June-25 June in the Annapolis and Saint John River valleys to after mid-July in parts of Newfoundland.